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    <title>Document</title>
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<body>
    <script>
        let chior= []; // 合唱团
        let duck = {
            duckSinging:function(){
                console.log('嘎嘎嘎');
            }
        }
        // 999
        for(let i= 0;i<999;i++){
            if(checkIsDuck(duck))
                chior.push(duck)
    }
    let chick = {
        // 只要有两条腿，并且嘎嘎嘎叫的就是鸭子
        duckSinging:function(){
            console.log('嘎嘎嘎')
        }
    }
    if (checkIsDuck(chick)){
        chior.push(chick);
    }
    
    /*
    *@func 检验是否是鸭子
    *@params obj{}
    *@return boolean
    */
    function checkIsDuck(obj){
        if(obj.hasOwnProperty('duckSinging')
        &&
        typeof obj.duckSinging == 'function'){
            return true;
        }
        return false;
    }
    if(chior.length >= 1000){
        console.log('招募工作已完成，')
    }
    </script>
</body>
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